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Effects of Gastric Bypass Surgery and Calcium Metabolism and the Skeleton

This study has been completed.
Information provided by (Responsible Party):
VA Office of Research and Development Identifier:
First received: April 5, 2011
Last updated: April 12, 2016
Last verified: April 2016
Obesity is a chronic illness of staggering proportions. Because weight loss through diet and exercise is difficult to attain and maintain, there has been escalating interest in bariatric surgery, including Roux-en-Y gastric bypass. Gastric bypass surgery results in long-term weight loss, dramatic improvement in comorbidities such as diabetes, and decreased mortality. Emerging evidence suggests, however, that gastric bypass may have negative effects on bone health. Because of the serious consequences of osteoporosis and fracture, this is of great concern. This study of the effects of gastric bypass on calcium metabolism and the skeleton may positively impact the clinical care of gastric bypass patients by their surgeons, primary care providers, and endocrinologists. Further, the knowledge gained may inform future investigation into the relationships between obesity, weight loss, and bone biology.

Obesity, Morbid Gastric Bypass

Study Type: Observational
Study Design: Observational Model: Cohort
Time Perspective: Prospective
Official Title: Effects of Gastric Bypass Surgery on Calcium Metabolism and the Skeleton

Resource links provided by NLM:

Further study details as provided by VA Office of Research and Development:

Primary Outcome Measures:
  • Change in Intestinal Calcium Absorption [ Time Frame: 6 months ]

    Change in fractional calcium absorption, determined by dual stable isotope method.

    Fractional calcium absorption is the fraction of ingested calcium that is absorbed, which is expressed here as the percentage of ingested calcium that is absorbed. The 6-month change is the mean difference in percentage absorption between time points. For example, if fractional calcium absorption were to decrease from 30% preoperatively to 25% at the 6-month postoperative time point, the change in fractional calcium absorption would be -5%.

Secondary Outcome Measures:
  • Bone Mineral Density (BMD, Areal and Volumetric) [ Time Frame: pre-operatively and 6 and 12 months post-operatively ]
    Areal BMD at the spine, proximal femur, and forearm by dual-energy X-ray absorptiometry (DXA); volumetric BMD at the spine and hip by quantitative computed tomography (QCT); volumetric BMD at the ultradistal radius and ultradistal tibia by high-resolution peripheral QCT (HR-pQCT)

  • Bone Structure [ Time Frame: pre-operatively and 6 and 12 months post-operatively ]
    Trabecular and cortical bone microstructure by HR-pQCT

Biospecimen Retention:   Samples Without DNA
serum, urine

Enrollment: 55
Study Start Date: July 2011
Study Completion Date: January 2015
Primary Completion Date: April 2014 (Final data collection date for primary outcome measure)
Gastric Bypass Surgery Patients
Obese men and women undergoing gastric bypass surgery


Ages Eligible for Study:   25 Years to 70 Years   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No
Sampling Method:   Non-Probability Sample
Study Population
Men and women 25 to 70 years old scheduled to undergo gastric bypass surgery

Inclusion Criteria:

Scheduled to undergo gastric bypass surgery. Please note that to be eligible, one must already be working with a bariatric surgeon and with plans in place to undergo gastric bypass. This study is unable to arrange or pay for gastric bypass surgery.

Exclusion Criteria:

  • Perimenopausal women
  • Known intestinal malabsorption
  • Prior bariatric surgery
  • Use of medications known to impact bone and mineral metabolism
  • Disease known to affect bone
  • Illicit drug use or alcohol use >3 drinks/day
  • Serum calcium >10.2 mg/dL
  • Calculated creatinine clearance <30 mL/min
  • Weight >350 pounds
  • Wrist circumference >12 inches or calf circumference >17 inches
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its identifier: NCT01330914

United States, California
San Francisco VA Medical Center, San Francisco, CA
San Francisco, California, United States, 94121
Sponsors and Collaborators
VA Office of Research and Development
Principal Investigator: Anne L Schafer, MD San Francisco VA Medical Center, San Francisco, CA
  More Information

Responsible Party: VA Office of Research and Development Identifier: NCT01330914     History of Changes
Other Study ID Numbers: ENDB-007-10F
1IK2CX000549-01 ( U.S. NIH Grant/Contract )
Study First Received: April 5, 2011
Results First Received: December 2, 2015
Last Updated: April 12, 2016

Keywords provided by VA Office of Research and Development:
Obesity, Morbid
Bariatric Surgery
Gastric Bypass
Calcium Metabolism Disorders
Vitamin D
Bone Density
Body Composition
Weight Loss

Additional relevant MeSH terms:
Obesity, Morbid
Nutrition Disorders
Body Weight
Signs and Symptoms
Calcium, Dietary
Bone Density Conservation Agents
Physiological Effects of Drugs processed this record on August 18, 2017